Today, wireless communication is widely used and a multitude of wireless communication systems have been developed to accomplish such communication. Well known wireless communication systems are e.g. the Global System for Mobile communications (GSM), the General Packet Radio Service (GPRS), the Universal Mobile Telecommunications System (UMTS) and other cellular technologies or similar. Other well known examples of wireless communication systems are the Wireless Local Access Networks (WLAN) and the Worldwide Interoperability for Microwave Access (WiMAX).
As is well known, the assignment of a relevant frequency spectrum resource to be used is a fundamental precondition for substantially any wireless communication system.
However, the usage of frequency spectrum has been liberalized in that frequency resources may no longer be exclusively assigned to a particular wireless communication system, largely based on the observation that frequency resources assigned by licenses to licensees are not used, e.g. not at all or not to the full extent. For example, one possible approach pursued in regulations is to license a frequency resource to a licensee (primary user), while the frequency resource can be simultaneously used by other users (secondary users) under the condition that they do not cause harmful interference to the wireless communication system of the primary user. In the future there will be a multitude of spectrum usage regimes applied for different resources/portions of the electro-magnetic spectrum.
One example is a dedicated licensed spectrum operation. Here, the licensee (typically the operator of the communication system in question) receives an exclusive license for using a certain spectrum resource for his communication system. The license is typically valid within a certain region and/or for a certain period of time. A dedicated licensed spectrum is e.g. used by today's 2G/3G cellular communication systems.
Another example is the licensed spectrum operation with opportunistic spectrum access by secondary user systems. Here, a primary user receives a non-exclusive license for using a certain spectrum resource for his communication system. The non-exclusive license is typically valid within a certain region and/or for a certain period of time. Other systems are allowed to use the licensed spectrum resource under a secondary license and/or under certain usage regimes. A secondary system may e.g. be required to sense if the primary system uses the spectrum resource. A detection of a primary usage—e.g. within a certain region and/or during a certain period of time—may require the secondary system to (at least temporarily) withhold from or cease usage of the licensed spectrum resource. This may e.g. be the case if the interference caused from the secondary system to the primary system exceeds a certain threshold. An example of the above can be found in the secondary usage of white space spectrum in US TV bands, as developed in IEEE 802.22.
Still another example is the licensed spectrum operation with allowance for spectrum trading. Here, a primary licensee receives an exclusive license for using a certain spectrum resource for his communication system with the option for renting out the usage of the licensed spectrum in exclusive secondary licenses. The license is typically valid within a certain region and/or for a certain period of time. A spectrum trading opportunity may e.g. occur when the primary licensee has the spectrum usage right for a certain spectrum resource in a specific region for 20 years, but is only using the spectrum at certain time periods. The primary user may then lease the temporal/regional usage of the spectrum resources to secondary users; e.g. on a yearly or monthly basis, or only during daily time periods. An example may be the renting of TV spectrum resource to cellular systems during times when no TV-programs are transmitted, e.g. during night.
Naturally, a further example is the un-licensed spectrum operation. Here, the usage of a certain spectrum resource is allowed to any system which fulfils certain usage regimes, e.g. maximum allowed transmission power, sharing rules, etc. The allowance is typically valid within a certain region and/or for a certain period of time.
Of course, the examples above are not exhaustive and the invention is applicable to other examples of spectrum usage, which may result in different availability and usability for a certain spectrum user.
It should be added that the frequency spectrum resources mentioned above may comprise any spectrum portion within which a wireless communication may be accomplished. In addition, a frequency spectrum resource may e.g. comprise a single continuous spectrum portion or several partitioned spectrum portions.
With the independence of spectrum usage from specific service types it is possible for communication systems to combine the usage of a multitude of spectrum resources, as long as the spectrum usage regime for each spectrum resource is applied. A service type may e.g. be the transmission of a message or similar (e.g. SMS, e-mail or similar), the transmission of voice and/or video or similar (e.g. conversations, music and/or movies or similar), or the transmission of data (e.g. data files or similar) etc. In addition, A service type may e.g. be broadcasted and/or unicasted or similar. The services may also be categorized in to Quality of Service (QoS) classes or similar, e.g. such as Conversational, Streaming, Interactive and Background or similar as defined by the standards of the 3GPP.
A spectrum-on-demand system can be defined as a system that acquires spectrum resources based on the current demand, i.e. a system that can acquire additional resources when this is considered to be beneficial. An example of a spectrum-on-demand system is a wireless communication system which, in addition to primary spectrum resources (possible exclusively licensed), makes use of secondary spectrum resources (typically not exclusively licensed) in case the current demand so requires. An exemplifying spectrum-on-demand system may e.g. have access to a primary spectrum resource on exclusive basis and to one or several secondary spectrum resource on opportunistic basis or similar. Another exemplifying spectrum-on-demand system may e.g. only have access to one or more secondary spectrum resource on opportunistic basis or similar.
An example of a spectrum-on-demand system is depicted in FIG. 1a. Here a spectrum resource aggregation function of a wireless communication system performs an aggregation of different spectrum resources F1-F4 and performs common resource management for these resources. One spectrum resource F1 may for example be the licensed spectrum of the operator of the communication system in question with exclusive usage right according to a dedicated licensed spectrum operation; another spectrum resource F2 may be available for the system in question with a temporarily exclusive usage right according to a secondary license that was bought from another communication system operator or a TV broadcast operator or similar; a third spectrum resource F3 may be available as a non-exclusively resource licensed by the operator of another system (e.g. a TV broadcast operator or a radar system) which is used opportunistically by the communication system in question; a fourth spectrum resource F4 can be available as an unlicensed spectrum resource that is used by an unknown amount of systems. Naturally, the spectrum resources F1-F4 may be of other types and there is nothing preventing that one or several of the spectrum resources are of the same type.
In a spectrum-on-demand system a common resource management is typically performed for the total resources comprising the different resource components provided by the individual spectrum resources. However, this does not exclude that further resource management functions are performed within each system resource, like for example, power control, congestion control, scheduling, resource-specific admission control, etc. The common resource management may e.g. include functions like common admission control of services, transmission capacity management and service allocation. The transmission capacity management comprises the capability to decide when to change the current transmission capacity situation, i.e. acquiring or releasing secondary spectrum resources. The service allocation comprises the capability to allocate different services to different spectrum resources.
In a spectrum-on-demand systems the amount of capacity that a particular spectrum resource can provide may fluctuate (e.g. according to external factors, like the number of other systems that make use of this spectrum or dynamic overhead for determining availability/usability of the spectrum resource). Thus, the transmission capacity required for a particular service may not be available at every instance of the lifetime of the session. For example, if many users are assigned to a variable spectrum resource it may happen that the negotiated bit rate and service performance is not achieved.
Hence, in view of the above there seems to be a need for improvements directed to the allocation of transmission capacity for the services provided in a wireless communication system.